The present invention relates to novel bisdithiophosphoric acid derivatives, to the use thereof as additives in lubricants, machining fluids and hydraulic fluids, and to compositions containing said derivatives.
Mixed oxothiophosphoric acids are disclosed as, lubricant additives in U.S. Pat. No. 4,544,492.
Methyl esters of formula 
Rxe2x80x22 are hydrocarbon radicals and Rxe2x80x23 is hydrogen or lower alkyl, are disclosed for the same utility in GB 1 347 845.
Dithiophosphoric acid derivatives which contain xe2x80x94Cxe2x95x90Cxe2x80x94 double bonds or xe2x80x94C(OH)xe2x80x94 groups are disclosed in U.S. Pat. No. 4,081.387.
Adducts of dithiophosphoric acids and acrylates are disclosed in U.S. Pat. No. 3,784,588. These adducts are esters of monohydric to hexahydric alcohols. The use of such compounds in hydraulic oils is disclosed in EP 465 156.
Surprisingly, it has been found that some esters of dihydric alcohols have particularly good properties as lubricant additives.
Specifically, the invention relates to compounds of formula 
wherein
R1 and R2 are each independently of the other C3-C18alkyl, C5-C12cycloalkyl,
C5-C6cycloalkylmethyl, C9-C10bicycloalkylmethyl, C9-C10tricycloalkylmethyl, phenyl,
C7-C24alkylphenyl or, taken together, are 
R3 is "Parenopenst"CH2"Parenclosest"b, C4-C40alkylene which is interrupted by xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, or xe2x80x94NR4xe2x80x94, or is a group of formula 
R4 is hydrogen, C1-C18alkyl, phenyl-C1-C4alkyl, phenyl or C1-C6alkyl-substituted phenyl,
R5 is hydrogen or methyl, and
b is an integer from 3 to 18.
Preferred compounds of formula I are those wherein R1 and R2 are each independently of the other C3-C10alkyl, C5-C6cycloalkyl, C5-C6cycloalkylmethyl, C9-C10bicycloalkylmethyl, C9-C10tricycloalkylmethyl, phenyl, C7-C18alkylphenyl or, taken together, are 
R3 is "Parenopenst"CH2"Parenclosest"b, C4-C20alkylene which is interrupted by xe2x80x94Oxe2x80x94 or NR4, or is a group of formula 
R4 is hydrogen or C1-C4alkyl, and b is an integer from 3 to 10, and compounds wherein R5 is hydrogen.
Also preferred are compounds wherein R3 is "Parenopenst"CH2"Parenclosest"b, C4-C12alkylene which is interrupted by xe2x80x94Oxe2x80x94 or NR4, or is 
R4 is C1-C4alkyl and b is an integer from 3 to 6.
Further preferred compounds are those wherein R1 and R2 are C3-C6alkyl.
b is preferably 4 to 6 and, most preferably, 4.
R4 is preferably hydrogen or C1-C4alkyl.
R1 and R2 defined in the above formulae as C3-C18alkyl are branched or unbranched radicals. Illustrative examples are propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl, 3-heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, 2-ethylbutyl, 1-methylpentyl, 1,3-dimethylbutyl, 1,1,3,3-tetramethylbutyl, 1-methylhexyl, isoheptyl, 1-methylheptyl, 1,1,3-trimethylhexyl or 1-methylundecyl.
R1 and R2 defined as C5-C12cycloalkyl may typically be cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl or cyclododecyl. Cyclopentyl and cyclohexyl are preferred. Cyclohexyl is most preferred.
R1 and R2 defined as C5-C6cycloalkylmethyl will be taken to mean cyclopentylmethyl and, preferably, cyclohexylmethyl.
R1 and R2 defined as C9-C10bicycloalkylmethyl are typically decalinylmethyl. R1 and R2 defined as C9-C10tricycloalkylmethyl are preferably a group of formula 
R1 and R2 defined as C9-C24alkylphenyl are phenyl groups which are substituted by one or more than one alkyl group, preferably by 1 to 3, most preferably 1 or 2, alkyl groups together containing 3 to 18 carbon atoms. Typical examples of such alkyl groups are methyl and ethyl and those cited above.
R1 and R2 are preferably identical.
Interrupted C4-C40alkylene R3 is preferably straight-chain and preferably contains ethylene units with alternating O, S or NR4. The interruption is preferably by oxygen, resulting in polyethylene glycol groups.
The invention further relates to compositions comprising
a) a lubricant, a machining fluid or hydraulic fluid, and
b) at least one compound of formula I as described above.
Preferred compositions are those wherein R1 and R2 are each independently of the other C3-C10alkyl, C5-C6-Cycloalkyl, C5-C6cycloalkylmethyl, C9-C10bicycloalkylmethyl, C9-C10tricycloalkylmethyl, phenyl, C7-C18alkylphenyl or, taken together, are 
R3 is "Parenopenst"CH2"Parenclosest"b, C4-C20alkylene which is interrupted by xe2x80x94Oxe2x80x94 or NR4, or is a group of formula 
R4 is hydrogen or C1-C4alkyl and b is an integer from 3 to 10.
Particularly preferred compositions are those wherein
R3 is "Parenopenst"CH2"Parenclosest"b, C4-C12alkylene which is interrupted by xe2x80x94Oxe2x80x94 or NR4, or is 
R4 is C1-C4alkyl and b is an integer from 3 to 6, and also compositions wherein R5 is hydrogen.
Compositions meriting special interest are those wherein R1 and R2 are C3-C6alkyl.
The lubricants, machining fluids or hydraulic fluids contained in the inventive compositions can decompose readily to a greater or lesser degree under the action of heat, mechanical stress (especially induced by shear forces) and chemical reagents (especially atmospheric oxygen).
The compounds of formula I afford protection against such influences and will conveniently be present in the novel compositions in amounts of 0.01 to 10% by weight, typically 0.05 to 5% by weight, preferably 0.05 to 3% by weight and, most preferably, 0.1 to 2% by weight. The novel compositions may contain one or more than one of these compounds, and the percentages by weight are based on the total amount of said compounds. The basis of calculation is the total weight of the lubricant, machining fluid or hydraulic fluid without the compounds of formula I.
The invention thus also relates to the use of compounds of formula I as additives for lubricants, hydraulic fluids and machining fluids, especially as extreme-pressure and antiwear additives as well as friction modifiers.
Such a utility also entails a process for enhancing the performance properties of lubricants, hydraulic fluids and machining fluids. The novel utility also encompasses the protection of the metal parts to be lubricated against mechanical wear (antiwear protection).
The suitable lubricants, hydraulic fluids and machining fluids are typically based on mineral or synthetic oils or mixtures thereof. The lubricants are known to the skilled person and are described in the relevant literature, inter alia in Dieter Klamann, xe2x80x9cSchmier-stoffe and verwandte Produktexe2x80x9d (Lubricants and Related Products) (Verlag Chemie, Weinheim, 1982), in Schewe-Kobek, xe2x80x9cDas Schmiermittel-Taschenbuchxe2x80x9d (Handbook of Lubricants) (Dr. Alfred Hxc3xcthig-Verlag, Heidelberg, 1974), and in xe2x80x9cUllmanns Enzyklopxc3xa4die der technischen Chemiexe2x80x9d (Ullmann""s Encyclopedia of Industrial Chemistry), Vol. 13, pages 85-94 (Verlag Chemie, Weinheim, 1977).
The lubricants are preferably oils and fats are typically derived from a mineral oil. Oils are preferred.
A further group of lubricants suitable for use in the practice of this invention comprises vegetable or animal oils, fats, tallows and waxes or mixtures with one another or with the mineral or synthetic oils referred to above. Vegetable and animal oils, fats, tallows and waxes are typically palm nut oil, palm oil, olive oil, beet oil, rapeseed oil, linseed oil, ground nut oil, soybean oil, cottonseed oil, sunflower seed oil, pumpkin seed oil, coconut oil, corn oil, castor oil, walnut oil and mixtures thereof, fish oils, the tallows of slaughter animals, e.g. beef tallow, neat""s foot and bone oil, as well as the modified, epoxidised and sulfoxidised forms thereof, typically epoxidised soybean oil.
The mineral oils are based in particular on hydrocarbon compounds.
Synthetic lubricants typically comprise lubricants based on aliphatic or aromatic carboxylates, polymeric esters, polyalkylene oxides, phosphates, poly-xcex1-olefins or silicones, on a diester of a divalent acid with a monohydric alcohol, typically dioctyl sebacate or dinonyl adipate, on a triester of trimethylolpropane with a monovalent acid or with a mixture of acids, conveniently trimethylolpropane tripelargonate, trimethylol-propane tricaprylate or mixtures thereof, on a tetraester of pentaerythritol with a monovalent acid or with a mixture of such acids, typically pentaerythritol tetracaprylate, or on a complex ester of monovalent and divalent acids with polyhydric alcohols, for example a complex ester of trimethylolpropane with caprylic and sebacic acid or of a mixture thereof. Especially suitable lubricants are, in addition to mineral oils, typically poly-xcex1-olefins, ester-based lubricants, phosphates, glycols, polyglycols and polyalkylene glycols and mixtures thereof with water.
Machining fluids and hydraulic fluids can be prepared from the same substances as those described above in connection with the lubricants. Often they are also emulsions of such substances in water or other liquids.
The lubricating compositions of this invention are used, inter alia, for combustion engines, typically for motor vehicles powered by engines of the Otto-cycle, diesel, two-stroke, Wankel or orbital type.
The compounds of formula I are readily soluble in lubricants, machining fluids and hydraulic fluids and are therefore especially suitable for use as additives for lubricants, machining fluids and hydraulic fluids. Their surprisingly good antiwear properties merit special mention.
The invention thus further relates to a process for enhancing the performance properties of lubricants, machining fluids and hydraulic fluids, which comprises adding thereto compounds of formula I.
The compounds of formula I can be blended with the lubricating compositions in a manner known per se. The compounds are, for example, readily soluble in oils. It is also possible to prepare a masterbatch, which can be diluted in accordance with consumption to suitable concentrations with the appropriate lubricant. In such cases, concentrations higher than 10% by weight are also possible.
The lubricants, machining fluids and hydraulic fluids of this invention may also contain other additives which are added for further enhancement of the basic properties. These further additives comprise antioxidants, metal deactivators, rust inhibitors, viscosity improvers, pour-point depressants, dispersants, detergents, other extreme-pressure and antiwear additives.